Clarify `lang/clone` docs
Clarify `lang/clone` docs

Specify that it will copy the object reference by default only if the type is
non-native.

mout/mout,millermedeiros/mout,MathiasPaumgarten/mout,MathiasPaumgarten/mout,mout/mout,Oyamasiphula/mout,millermedeiros/mout,stevemao/mout,ChristianGrete/mout,ChristianGrete/mout,Oyamasiphula/mout,stevemao/mout